Referring to FIGS. 1 to 5, a conventional method for generating a network topology (a method used in the “Gnutella”) will be explained. To be more specific, an operation in which a node 105 newly joins a network including nodes 101 to 104.
First, as shown in FIG. 1, the node 105 selects a node 101 which IP address or URL the node 105 knows, among from a plurality of nodes 101 to 104 which forms the network, so as to establish a connection with the node 101.
Second, as shown in FIG. 2, the node 105 transmits a PING message including an IP address of the node 105 to the node 101.
Third, as shown in FIG. 3, the node 101 returns a PONG message including an IP address of the node 101 to the node 105, and transfers the PING message including the IP address of the node 105 to nodes 102 to 104.
Fourth, as shown in FIG. 4, each of the nodes 112 to 104 returns PONG messages Including respective IP addresses to the node 105.
The node 105 can acquire the IP address of nodes in the range designated in the TTL (Time to Live) field of the PING message, by repeating the above mentioned procedure.
Fifth, as shown in FIG. 5, the node 105 establishes connections with each of the nodes 101 to 104 which forms the network by referring to the IP address included in the received PONG messages.
Thus, the node 105 can newly join the network formed by the nodes 101 to 104.
As mentioned above, in the conventional method for generating a network topology, the new node 105 is configured to join the network randomly, by using the PING message and the PONG message.
However, In the conventional method for generating a network topology a network condition in a physical layer is not considered, upon generating a new network topology. Therefore, there is a possibility that a network delay is considerably large between adjacent nodes in a logical layer, and there is a possibility that data transfer efficiency is reduced in a newly generated network.
(Patent Literature 1) JP2003-304277
In viewing of the foregoing, it is an object of the present Invention to provide a network topology generation method and a node which can reduce a network delay fairly and minimally, upon generating a new network topology, by considering a network condition in a physical layer